IO2 THE BEHAVIOR OF LOWER ORGANISMS. 



electric current are not found in the reactions to other stimuli, it seems 

 a perversion to make the electric reaction a type for all others. The 

 reaction of the infusoria to the electric current takes in its characteristic 

 features a unique position among the reactions of the organism, requiring 

 special explanation. 



(3) In the response of the infusoria to the electric current there 

 appears also the same type of reaction that occurs as a response to other 

 stimuli, but obscured by the phenomena peculiar to the effects of the 

 current. 



This fact, that the reaction to the electric current is of a dual char- 

 acter, that the peculiar effects of the current are, as it were, superposed 

 upon the usual method of reaction, is not usually so clearly recognized 

 as it deserves to be. 



If the constant current is passed through a preparation containing 

 large numbers of some species of the Hypotricha, as Stylonychia or 

 Oxytricha, it will be found that the animals, practically without excep- 

 tion, attain their orientation by turning toward the right side, thus 

 reacting as they would to any other stimulus. Further, if after they 

 are oriented the direction of the current is reversed, the animals all, 

 without exception, attain their new orientation (with anterior ends in 

 the opposite direction) by whirling toward their right sides. Thus, so 

 far, the reaction to the electric current is identical with that to other 

 stimuli, and the direction of turning is determined by an internal factor, 

 not by the way in which the current strikes the organism. In these 

 respects the Hypotricha agree with the Rotifera. 



But exact observation shows that in the Hypotricha there is another 

 factor involved in the reaction. The characteristic polarizing effect of 

 the current appears in its action on the motor organs that are distributed 

 over the body surface ; those on one half of the body strike in one 

 direction, those on the other half in the opposite direction. Part of 

 these motor organs, therefore, assist in turning the organism in its usual 

 way (to the right) ; part oppose this turning. The result is that in 

 certain positions the turning to the right is opposed by the stroke of a 

 large number of cilia, so that the turning takes place more slowly than 

 usual. Nevertheless, in the Hypotricha, the determining factor in the 

 reaction to the electric current is almost throughout the same as in 

 the reaction to other stimuli ; the direction of turning is determined by 

 internal factors, as a reaction of the whole organism, not by the direction 

 in which the current strikes or passes through the organism. (Details 

 in the work of Pearl, 1900.) 



If in place of one of the Hypotricha we experiment with an infusorian 

 in which the cilia cover closely the whole surface of the body, as Para- 

 mecium, the peculiar polarizing effect of the current on the cilia of the 



